An automatic transmission of a vehicle uses pressurized oil in order to actuate the clutches and gear speed change mechanism of the automatic transmission. An automatic transmission may include an oil supply system including an oil pump for supplying the pressurized oil. Typically, the oil pump is mechanically driven by the vehicle drive. If the vehicle drive is the internal combustion engine, the oil pump may be driven by the crankshaft. In systems in which the oil pump is mechanically driven by the crankshaft, there is a delay between the initial start up of the engine that causes the crankshaft to rotate and drive the mechanical pump at a sufficient rpm (revolutions per minute) to supply oil to the automatic transmission at a pressure that is sufficient to actuate the clutch and allow the vehicle to move forward.
US 2009/0118878 A1 discloses an oil system for a vehicle that includes an external electrically driven oil pump as well as a mechanically driven oil pump for a hybrid electric vehicle having an automatic transmission. The external electrically driven oil pump can be used during initial start up as well as running of vehicle. This system may provide a more rapid response by preferably supplying a sufficient amount of oil to a transmission and engine clutch in the case of a quick start after a vehicle stop. However, the use of an additional external electrically driven oil pump has the disadvantage that this further component increases the complexity of the oil supply system due to the additional connections between the external oil pump and the oil supply system. The further component also increases the size of the oil supply system.
In view of the foregoing, it is desirable to provide an oil supply system for an automatic transmission in which an electrical pump can be more simply and compactly accommodated. In addition, other desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.